Multi-speed transmission

ABSTRACT

A transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may include clutches and at least one brake.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent Ser. No. 12/020,315, filed on Jan. 25, 2008, which claims the benefit of U.S. Provisional Application No. 60/912,764 filed on Apr. 19, 2007. The disclosure of the above application is incorporated herein by reference.

FIELD

The invention relates generally to a multiple speed transmission having a plurality of planetary gear sets and a plurality of torque transmitting devices and more particularly to a transmission having eight or more speeds, four planetary gear sets and a plurality of torque transmitting devices.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.

A typical multiple speed transmission uses a combination of friction clutches, planetary gear arrangements and fixed interconnections to achieve a plurality of gear ratios. The number and physical arrangement of the planetary gear sets, generally, are dictated by packaging, cost and desired speed ratios.

While current transmissions achieve their intended purpose, the need for new and improved transmission configurations which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness and improved packaging, primarily reduced size and weight, is essentially constant. Accordingly, there is a need for an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling or rotary members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices are for example clutches and brakes.

Further features, aspects and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature.

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way;

FIG. 1 is a lever diagram of an embodiment of an eight speed transmission according to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of an eight speed transmission according to the present invention; and

FIG. 3 is a truth table presenting the state of engagement of the various torque transmitting elements in each of the available forward and reverse speeds or gear ratios of the transmission illustrated in FIGS. 1 and 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that the embodiments of the transmission of the present invention have an arrangement of permanent mechanical connections between the elements of the four planetary gear sets. These mechanical connections generically link or relate the transmission embodiments. More specifically, a first component or element of a first planetary gear set is permanently coupled to a ground or a transmission housing. A second component or element of the first planetary gear set is permanently coupled to a second component or element of a second planetary gear set. A first component or element of the second planetary gear set is permanently coupled to a first component or element of a third planetary gear set. A second component or element of the third planetary gear set is permanently coupled to a second component or element of a fourth planetary gear set. A third component or element of the first planetary gear set is permanently coupled to a third component or element of the fourth planetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10 is illustrated in a lever diagram format. A lever diagram is a schematic representation of the components of a mechanical device such as an automatic transmission. Each individual lever represents a planetary gear set wherein the three basic mechanical components of the planetary gear are each represented by a node. Therefore, a single lever contains three nodes: one for the sun gear, one for the planet gear carrier, and one for the ring gear. The relative length between the nodes of each lever can be used to represent the ring-to-sun ratio of each respective gear set. These lever ratios, in turn, are used to vary the gear ratios of the transmission in order to achieve an appropriate ratios and ratio progression. Mechanical couplings or interconnections between the nodes of the various planetary gear sets are illustrated by thin, horizontal lines and torque transmitting devices such as clutches and brakes are presented as interleaved fingers. If the device is a brake, one set of the fingers is grounded. Further explanation of the format, purpose and use of lever diagrams can be found in SAE Paper 810102, “The Lever Analogy: A New Tool in Transmission Analysis” by Benford and Leising which is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a first planetary gear set 14 having three nodes: a first node 14A, a second node 14B and a third node 14C, a second planetary gear set 16 having three nodes: a first node 16A, a second node 16B and a third node 16C, a third planetary gear set 18 having three nodes: a first node 18A, a second node 18B and a third node 18C, a fourth planetary gear set 20 having three nodes: a first node 20A, a second node 20B and a third node 20C and an output shaft or member 22.

The first node 14A of the first planetary gear set 14 is coupled to ground, a stationary element or the transmission housing 50. The second node 14B of the first planetary gear set 14 is coupled to the first node 20A of the fourth planetary gear set 20. The third node 14C of the first planetary gear set 14 is coupled to first node 16A of the second planetary gear set 16. The third node 16C of the second planetary gear set 16 is coupled to third node 18C of the third planetary gear set 18. The first node 18A of the third planetary gear set 18 is coupled to the third node 20C of the fourth planetary gear set 20. The second node 16B of the second planetary gear set 16 is coupled to the input shaft or member 12.

A first clutch 26 selectively connects the second node 16B of the second planetary gear set 16 to the first node 18A of the third planetary gear set 18. A second clutch 28 selectively connects the third node 16C of the second planetary gear set 16 and the third node 18C of the third planetary gear set 18 to the first node 18A of the third planetary gear set 18. A third clutch 30 selectively connects the second node 18B of the third planetary gear set 18 to the output shaft or member 22. A fourth clutch 32 selectively connects the second node 20B of the fourth planetary gear set 20 to the output shaft or member 22. A brake 34 selectively connects the third node 14C of the first planetary gear set 14 to the ground, stationary element or transmission housing 50.

Referring now to FIG. 2, a stick diagram presents a schematic layout of the embodiment of the eight speed transmission 10 according to the present invention. In FIG. 2, the numbering from the lever diagram of FIG. 1 is carried over. The clutches, brake and couplings are correspondingly presented whereas the nodes of the planetary gear sets now appear as components of planetary gear sets such as sun gears, ring gears, planet gears and planet gear carriers.

For example, the first planetary gear set 14 includes a sun gear member 14C, a planet gear carrier member 14B that rotatably supports a set of planet gears 14D and a ring gear member 14A. Planet gears 14D are each configured to intermesh with both sun gear member 14C and ring gear member 14A. Sun gear member 14C is connected for common rotation with a first interconnecting shaft or member 46 and a second interconnecting shaft or member 52. Ring gear member 14A is connected to the ground, stationary element or transmission housing 50 through a third interconnecting shaft or member 47. The planet gear carrier member 14B is connected for common rotation with a fourth interconnecting shaft or member 48.

The input shaft or member 12 is preferably continuously connected to an engine (not shown) or to a turbine of a torque converter (not shown). The output shaft or member 22 is preferably continuously connected with the final drive unit or transfer case (not shown).

Planetary gear set 16 includes a sun gear member 16A, a planet carrier member 16B that rotatably supports a set of planet gears 16D and a ring gear member 16C. Sun gear member 16A is connected for common rotation with second interconnecting shaft or member 52. Planet carrier member 16B is connected for common rotation with input shaft or member 12 and a fifth interconnecting shaft or member 54. Ring gear member 16C is connected for common rotation with a sixth interconnecting shaft or member 56. Planet gears 16D are each configured to intermesh with both sun gear member 16A and ring gear member 16C.

Planetary gear set 18 includes a sun gear member 18C, a ring gear member 18A and a planet carrier member 18B that rotatably supports a set of planet gears 18D. Sun gear member 18C is connected for common rotation with sixth interconnecting shaft or member 56. Ring gear member 18A is connected for common rotation with a seventh interconnecting shaft or member 58 and a ninth interconnecting shaft or member 59. Planet carrier member 18B is connected for common rotation with an eighth interconnecting shaft or member 60. Planet gears 18D are each configured to intermesh with both sun gear member 18C and ring gear member 18A.

Planetary gear set 20 includes a sun gear member 20C, a ring gear member 20A and a planet carrier member 20B that rotatably supports a set of planet gears 20D. Sun gear member 20C is connected for common rotation with ninth interconnecting shaft or member 59. Ring gear member 20A is connected for common rotation with fourth interconnecting shaft or member 48. Planet carrier member 20B is connected for common rotation with a tenth interconnecting shaft or member 62. Planet gears 20D are each configured to intermesh with both sun gear member 20C and ring gear member 20A.

The torque-transmitting mechanisms or clutches 26, 28, 30, 32 and brake 34 allow for selective interconnection of the shafts or interconnecting members, members of the planetary gear sets and the housing. For example, first clutch 26 is selectively engageable to connect ring gear member 18A and seventh interconnecting shaft or member 58 to fifth interconnecting shaft or member 54. Second clutch 28 is selectively engageable to connect seventh interconnecting shaft or member 58 to sixth interconnecting shaft or member 56. Third clutch 30 is selectively engageable to connect output shaft or member 22 to eighth interconnecting shaft or member 60. Fourth clutch 32 is selectively engageable to connect tenth interconnecting shaft or member 62 to output shaft or member 22. Brake 34 is selectively engageable to connect first interconnecting shaft or member 46 to transmission housing 50 to restrict rotation of first interconnecting shaft or member 46 relative to transmission housing 50.

Referring now to FIGS. 2 and 3, the operation of the embodiment of the eight speed transmission 10 will be described. It will be appreciated that transmission 10 is capable of transmitting torque from the input shaft or member 12 to the output shaft or member 22 in at least eight forward speed or torque ratios and at least one reverse speed or torque ratio. Each forward and reverse speed or torque ratio is attained by engagement of one or more of the torque-transmitting mechanisms (i.e. first clutch 26, second clutch 28, third clutch 30, fourth clutch 32 and brake 34), as will be explained below. FIG. 3 is a truth table presenting the various combinations of torque-transmitting mechanisms that are activated or engaged to achieve the various gear states. Actual numerical gear ratios of the various gear states are also presented although it should be appreciated that these numerical values are exemplary only and that they may be adjusted over significant ranges to accommodate various applications and operational criteria of the transmission 10. Examples of the gear ratios that may be obtained using the embodiments of the present invention are also shown in FIG. 3. Of course, other gear ratios are achievable depending on the gear diameter, gear teeth count and gear configuration selected.

To establish reverse gear, third clutch 30, fourth clutch 32 and brake 34 are engaged or activated. Third clutch 30 connects output shaft or member 22 to eighth interconnecting shaft or member 60. Fourth clutch 32 connects output shaft or member 22 to tenth interconnecting shaft or member 62. Brake 34 connects first interconnecting shaft or member 46 to transmission housing 50 to restrict rotation of first interconnecting shaft or member 46 and sun gear 14C relative to transmission housing 50. Likewise, the eight forward ratios are achieved through different combinations of clutch and brake engagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation and gear states of the eight speed transmission 10 assumes, first of all, that all the clutches and the brake not specifically referenced in a given gear state are inactive or disengaged and, second of all, that during gear shifts, i.e., changes of gear state, between at least adjacent gear states, a clutch or brake engaged or activated in both gear states will remain engaged or activated.

The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 

1. A transmission comprising: an input member; an output member; first, second, third and fourth planetary gear sets each having first, second and third members; a first torque transmitting mechanism selectively engageable to interconnect the first member of the first planetary gear set with a stationary element; a second torque transmitting mechanism selectively engageable to interconnect the second member of the second planetary gear set with the third member of the third planetary gear set; a third torque transmitting mechanism selectively engageable to interconnect at least one of the third member of the second planetary gear set and the first member of the third planetary gear set with the third member of the third planetary gear set; a fourth torque transmitting mechanism selectively engageable to interconnect the second member of the third planetary gear set with the output member; and a fifth torque transmitting mechanism selectively engageable to interconnect the second member of the fourth planetary gear set with the output member, and wherein the torque transmitting mechanisms are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.
 2. The transmission of claim 1 wherein the first members are sun gears, the second members are carrier members, and the third members are ring gears.
 3. The transmission of claim 1 wherein the input member is continuously interconnected with the second member of the second planetary gear set.
 4. The transmission of claim 1 wherein the stationary element is a transmission housing.
 5. The transmission of claim 1 wherein the at least one reverse speed ratio is achieved by engagement of the first, fourth, and fifth torque transmitting mechanisms.
 6. The transmission of claim 5 wherein a first of the at least eight forward speed ratios is achieved by engagement of the first, second, and fifth torque transmitting mechanisms.
 7. The transmission of claim 6 wherein a second of the at least eight forward speed ratios is achieved by engagement of the first, third, and fifth torque transmitting mechanisms.
 8. The transmission of claim 7 wherein a third of the at least eight forward speed ratios is achieved by engagement of the second, third and fifth torque transmitting mechanisms.
 9. The transmission of claim 8 wherein a fourth of the at least eight forward speed ratios is achieved by engagement of the third, fourth and fifth torque transmitting mechanisms.
 10. The transmission of claim 9 wherein a fifth of the at least eight forward speed ratios is achieved by engagement of the second, fourth and fifth torque transmitting mechanisms.
 11. The transmission of claim 10 wherein a sixth of the at least eight forward speed ratios is achieved by engagement of the second, third and fourth torque transmitting mechanisms.
 12. The transmission of claim 11 wherein a seventh of the at least eight forward speed ratios is achieved by engagement of the first, second and fourth torque transmitting mechanisms.
 13. The transmission of claim 12 wherein an eighth of the at least eight forward speed ratios is achieved by engagement of the first, third, and fourth torque transmitting mechanisms.
 14. The transmission of claim 1 wherein the third member of the first planetary gear set and the stationary element form a non-rotary member, the second member of the first planetary gear set and the third member of the fourth planetary gear set form a first rotary member, the first member of the first planetary gear set and the first member of the second planetary gear set form a second rotary member, the third member of the second planetary gear set and the first member of the third planetary gear set form a third rotary member, and the third member of the third planetary gear set and the first member of the fourth planetary gear set form fourth rotary member.
 15. A transmission comprising: an input member; an output member; first, second, third and fourth planetary gear sets each having a sun gear, a carrier member, and a ring gear wherein the input member is continuously interconnected with the carrier member of the second planetary gear set; at least five continuous interconnections from at least one of the sun gears, carrier members, and ring gears to at least one other of the sun gears, carrier members, ring gears, and a stationary member; a first torque transmitting mechanism selectively engageable to interconnect the sun gear of the first planetary gear set with the stationary member; a second torque transmitting mechanism selectively engageable to interconnect the carrier member of the second planetary gear set with the ring gear of the third planetary gear set; a third torque transmitting mechanism selectively engageable to interconnect at least one of the ring gear of the second planetary gear set and the sun gear of the third planetary gear set with the ring gear of the third planetary gear set; a fourth torque transmitting mechanism selectively engageable to interconnect the carrier member of the third planetary gear set with the output member; and a fifth torque transmitting mechanism selectively engageable to interconnect the carrier member of the fourth planetary gear set with the output member, and wherein the torque transmitting mechanisms are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.
 16. The transmission of claim 15 wherein a first of the five interconnecting members continuously interconnects the ring gear of the first planetary gear set with the stationary member, a second of the five interconnecting members continuously interconnects the carrier member of the first planetary gear set with the ring gear of the fourth planetary gear set, a third of the five interconnecting members continuously interconnects the sun gear of the first planetary gear set with the sun gear of the second planetary gear set, a fourth of the five interconnecting members continuously interconnects the ring gear of the second planetary gear set with the sun gear of the third planetary gear set, and a fifth of the five interconnecting members continuously interconnects the ring gear of the third planetary gear set with the sun gear of the fourth planetary gear set.
 17. The transmission of claim 15 wherein the at least one reverse speed ratio is achieved by engagement of the first, fourth, and fifth torque transmitting mechanisms.
 18. The transmission of claim 17 wherein a first of the at least eight forward speed ratios is achieved by engagement of the first, second, and fifth torque transmitting mechanisms.
 19. The transmission of claim 18 wherein a second of the at least eight forward speed ratios is achieved by engagement of the first, third, and fifth torque transmitting mechanisms.
 20. The transmission of claim 19 wherein a third of the at least eight forward speed ratios is achieved by engagement of the second, third and fifth torque transmitting mechanisms.
 21. The transmission of claim 20 wherein a fourth of the at least eight forward speed ratios is achieved by engagement of the third, fourth and fifth torque transmitting mechanisms.
 22. The transmission of claim 21 wherein a fifth of the at least eight forward speed ratios is achieved by engagement of the second, fourth and fifth torque transmitting mechanisms.
 23. The transmission of claim 22 wherein a sixth of the at least eight forward speed ratios is achieved by engagement of the second, third and fourth torque transmitting mechanisms.
 24. The transmission of claim 23 wherein a seventh of the at least eight forward speed ratios is achieved by engagement of the first, second and fourth torque transmitting mechanisms.
 25. The transmission of claim 24 wherein an eighth of the at least eight forward speed ratios is achieved by engagement of the first, third, and fourth torque transmitting mechanisms. 